Field of the Invention
The present invention relates to motor vehicle tyres. In particular, the present invention relates to a pair of tyres intended to be respectively mounted on the front and rear wheels of “supersport” motor vehicles having large engine capacity (e.g. 600 cm3 or higher), and/or high power (e.g. 170-180 hp or higher), also used on tracks.
Description of the Related Art
In recent times a trend has been observed to introduce in the market motor vehicles for supersport use having increasingly high power. For example, motor vehicles for road use having an engine capacity of 1000 cm3, with powers of 180 hp, are in fact already available on the market.
For ensuring such high performances, the tyres mounted on the wheels of such motor vehicles shall have very good features as regards the grip to the ground, so as to be able to effectively transfer the high traction torque to the ground, both while running on a straight path and while accelerating on leaving a bend, as well as to ensure an effective braking action. The grip becomes a really critical issue above all when running on wet road surfaces.
For ensuring to the motorcyclist that such performances are reached in a fully safe condition, the tyres shall ensure, together with a very good grip to the ground, behaviour stability both while running on a straight path and while running on bends, particularly in conditions of high acceleration/deceleration. In fact, a stable behaviour of the tyre indicates its capacity to effectively dampen perturbations transmitted by the unevenness of the road surface while running, so that such perturbations are not propagated to the motor vehicle, thus compromising the driving stability.
Among the features that the tyres shall ensure, the water draining is particularly important in the specific case of tyres for front wheels. An effective water draining of the front tyre allows the rear tyre to run on a straight path on drained asphalt, so as to effectively transfer the power to the ground.
In the specific case of tyres for rear wheels are instead particularly important, besides the grip to the ground and draining, the behaviour stability and the wear evenness.
Generally, in order to meet at least some of the aforementioned needs, a plurality of grooves is formed on the tread band, which grooves substantially extend from the central annular portion of the tread band up to the opposite shoulder annular portions.
The behaviour of the tyre while running is in fact greatly influenced by the number, orientation, arrangement and shape of such grooves, i.e. by the specific pattern of the tread band.
EP1826026 describes a tyre for a two-wheeled vehicles comprising a tread band provided with a pair of circumferential grooves extending substantially in a circumferential direction of the tyre and oppositely disposed to the equatorial plane (CL) of the tyre, and a plurality of inclined grooves extending from an outer side to an inner side in a width direction on a grounding surface of a tread band portion to be inclined with respect to a circumferential direction of the tyre and ended within the grounding surface of the tread band. The inclined grooves slant in mutually opposite directions with respect to the circumferential direction and are alternatively arranged along the circumferential direction of the tyre. At least some of the inclined grooves extend across the equatorial plane of the tyre.
EP906836 describes a tyre for a two-wheeled vehicle comprising a tread band having at least one groove extending axially from the tread centre to the tread edges. In a first axial region of the tread band, which is the central region of the tread band and is intended to contact the ground when moving in a straight line, the groove is arranged substantially circumferentially. In a second axial region at the axial edge of tread band, which is the region intended to contact the ground when the vehicle is cornering at the maximum camber angle, the alignment of the grooves is substantially transverse. In a third axial region, which is the region of the tread band between the first central region and the second region, and which is the region intended to contact the ground when the vehicle is cornering at a camber angle less than the maximum one, the alignment changes progressively axially outwardly from substantially circumferential to substantially transverse so that in the first, second and third axial regions of the tread band the grooves are substantially aligned with the resultant forces acting on the tread band surface in the contact region between the tread band and the ground.